Illinois Basin - Boundaries and Sedimentary Rocks

Boundaries and Sedimentary Rocks

The basin is bordered on the northeast by the Kankakee Arch, on the southeast by the Cincinnati Arch, on the south by the Pascola Arch, on the southwest by the Ozark Dome, on the northwest by the Mississippi River Arch, and on the north by the Wisconsin Arch. The New Madrid Seismic Zone and the Wabash Valley Seismic Zone intersect the southern portion of the basin.

At its center beneath southern Illinois, the basin contains a thickness of about 15,000 feet of Cambrian through Pennsylvanian sedimentary rocks, predominantly marine, and mostly dolomite, limestone, shale, and sandstone.

The basement rocks deep below the sedimentary rocks of the basin are Proterozoic granites and rhyolite of the Eastern Granite–Rhyolite Province which dates to around 1.55 Ga.